Provided herein are processes for the preparation of alkoxycarbonyl isothiocyanate.
U.S. Pat. No. 8,143,395 describes a process for the preparation of 5-substituted-8-alkoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-amines efficiently and in high yield by a manufacturing process that avoids hydrazine and cyanogen halide. The first step of the process requires an alkoxycarbonyl isothiocyanate starting material of the formula
in which R represents C1-C4 alkyl.
U.S. Pat. No. 4,659,853 teaches that alkoxycarbonyl isothiocyanate can be generated using an organic solvent, including aromatic hydrocarbons such as toluene. However, the addition of a co-solvent such as acetonitrile is needed for improvement of reaction rates and yield.
U.S. Pat. No. 4,778,921 teaches that alkoxycarbonyl isothiocyanate can be generated using water alone as the solvent system. U.S. Pat. No. 5,194,673 teaches that co-catalysts such as sodium or potassium acetate accelerate the rate of alkoxycarbonyl isothiocyanate generation when using water alone as the solvent system. However, isolating alkoxycarbonyl isothiocyanate from aqueous solutions generally results in decomposition and thus lower usable yields of product.
It would be advantageous to produce alkoxycarbonyl isothiocyanates efficiently, at faster rate and in high yield free of the decomposition products such as hydrogen sulfide, carbamates and alkyl chlorides.